1. Field of the Invention
The present invention relates to magnetic recording media for optomagnetic memory devices, magnetic recording devices, and display elements, and more particularly to improvements in optomagnetic recording media from which the stored information can be read out by utilizing a magnetooptic effect such as the Kerr effect or the Faraday effect.
2. Description of the Prior Art
Various optomagnetic recording media are known, including, for example; polycrystalline thin films of MnBi and MnCuBi; amorphous thin films of GdCo, GdFe, TdFe, DyFe, GdTbFe, TbDyFe, GdFeCo, TbFeCo, and GdTbCo; and a single-crystalline film of GdIG.
Of these films, the amorphous films are regarded today as superior optomagnetic recording media, in view of their film-forming property which permits them to be made up into large area films at room temperature or around it, their effectiveness for writing signals with small quantities of thermal energy generated by irradiation of light, and their effectiveness for reading the written signals in high S/N ratios. In particular, GdTbFe is best suited for optomagnetic recording media because of its large Kerr rotation angle and its Curie point of about 150.degree. C.
However, the amorphous magnetic materials used for magnetic recording media including GdTbFe have the drawback of low corrosion resistance. That is, these materials, in contact with the atmosphere or water vapor slowly, deteriorate in magnetic properties and finally are completely oxidized and become transparent.
For the purpose of eliminating this drawback, there have been proposed to date for example, an optomagnetic recording medium having a transparent protective layer of SiO.sub.2, SiO, or the like on the upper side of the recording layer and a recording medium in disk form sealed in inert gas.
These magnetic recording media, however, are unsatisfactory in corrosion resistance, still having the drawback of being subject to oxidation, which corrosion thereby causes the media to deteriorate in magnetic properties.